1.引言
2.实现代码
2.1.服务器端代码
2.1.1. 文件上传状态类(FileUploadStatus)
2.1.2. 文件上传状态侦听类(FileUploadListener)
2.1.3. 后台服务类(BackGroundService)
2.1.4. 文件上传状态控制类(BeanControler)
2.2. 客户端代码
2.2.1. AjaxWrapper.js
2.2.2. fileUpload.html
2.2.3. result.jsp
2.2.4. fileUpload.css
2.3. 配置文件
3. 结语

 1. 引言

   基于浏览器的文件上传,特别是对于通过<input type="file">标签来实现上传的情况, 存在着严重的性能问题,因为用户提交了文件之后,在浏览器把文件上传到服务器的过程中,界面看上去似乎是静止的,如果是小文件还好些,如果不幸需要上传的是几兆、几十兆甚至上百兆的文件,我相信那是一种非常痛苦的体验,我们中间的很多人应该都有过此种不堪的经历。(一笑)

  现在我就针对这个问题给出一个解决方案,我们将实现一个具有监控能力的WEB上传的程序——它不仅把文件上传到服务器,而且"实时地"监视文件上传的实际过程。

解决方案的基本思路是这样的:

  •   在Form提交上传文件同时,使用AJAX周期性地从Servlet轮询上传状态信息
  •   然后,根据此信息更新进度条和相关文字,及时反映文件传输状态
  •   如果用户取消上传操作,则进行相应的现场清理工作:删除已经上传的文件,在Form提交页面中显示相关信息
  •   如果上传完毕,显示已经上传的文件内容(或链接)

在介绍源代码之前,我们先来看看程序运行界面:

 2. 实现代码

   实现代码想当然的有服务器端代码和客户端代码(呵呵),我们先从服务器端开始。

 2.1. 服务器端代码

  2.1.1. 文件上传状态类(FileUploadStatus)

   使用FileUploadStatus这个类记录文件上传状态,并将其作为服务器端与web客户端之间通信的媒介,通过对这个类对象提供上传状态作为服务器回应发送给web客户端, web客户端使用JavaScript获得文件上传状态。源代码如下:

/**
 * 本例程演示了通过Web上传文件过程中的进度显示。您可以对本例程进行任何修改和使用。
 * 如果需要转载本例程,请您注明作者。
 *
 * 作者: 刘作晨
 * EMail:liuzuochen@gmail.com
 */
package liuzuochen.sample.upload;
import java.util.*;
public class FileUploadStatus {
  //上传用户地址
  private String uploadAddr;
  //上传总量
  private long uploadTotalSize = 0;
  //读取上传总量
  private long readTotalSize = 0;
  //当前上传文件号
  private int currentUploadFileNum = 0;
  //成功读取上传文件数
  private int successUploadFileCount = 0;
  //状态
  private String status = "";
  //处理起始时间
  private long processStartTime = 0l;
  //处理终止时间
  private long processEndTime = 0l;
  //处理执行时间
  private long processRunningTime = 0l;
  //上传文件URL列表
  private List uploadFileUrlList = new ArrayList();
  //取消上传
  private boolean cancel = false;
  //上传base目录
  private String baseDir = "";
  public FileUploadStatus() {
  }
  public String getBaseDir() {
    return baseDir;
  }
  public void setBaseDir(String baseDir) {
    this.baseDir = baseDir;
  }
  public boolean getCancel() {
    return cancel;
  }
  public void setCancel(boolean cancel) {
    this.cancel = cancel;
  }
  public List getUploadFileUrlList() {
    return uploadFileUrlList;
  }
  public void setUploadFileUrlList(List uploadFileUrlList) {
    this.uploadFileUrlList = uploadFileUrlList;
  }
  public long getProcessRunningTime() {
    return processRunningTime;
  }
  public void setProcessRunningTime(long processRunningTime) {
    this.processRunningTime = processRunningTime;
  }
  public long getProcessEndTime() {
    return processEndTime;
  }
  public void setProcessEndTime(long processEndTime) {
    this.processEndTime = processEndTime;
  }
  public long getProcessStartTime() {
    return processStartTime;
  }
  public void setProcessStartTime(long processStartTime) {
    this.processStartTime = processStartTime;
  }
  public long getReadTotalSize() {
    return readTotalSize;
  }
  public void setReadTotalSize(long readTotalSize) {
    this.readTotalSize = readTotalSize;
  }
  public int getSuccessUploadFileCount() {
    return successUploadFileCount;
  }
  public void setSuccessUploadFileCount(int successUploadFileCount) {
    this.successUploadFileCount = successUploadFileCount;
  }
  public int getCurrentUploadFileNum() {
    return currentUploadFileNum;
  }
  public void setCurrentUploadFileNum(int currentUploadFileNum) {
    this.currentUploadFileNum = currentUploadFileNum;
  }
  public String getStatus() {
    return status;
  }
  public void setStatus(String status) {
    this.status = status;
  }
  public long getUploadTotalSize() {
    return uploadTotalSize;
  }
  public String getUploadAddr() {
    return uploadAddr;
  }
  public void setUploadTotalSize(long uploadTotalSize) {
    this.uploadTotalSize = uploadTotalSize;
  }
  public void setUploadAddr(String uploadAddr) {
    this.uploadAddr = uploadAddr;
  }
  public String toJSon() {
    StringBuffer strJSon = new StringBuffer();
    strJSon.append("{UploadTotalSize:").append(getUploadTotalSize()).append(
        ",")
        .append("ReadTotalSize:").append(getReadTotalSize()).append(",")
        .append("CurrentUploadFileNum:").append(getCurrentUploadFileNum()).
        append(",")
        .append("SuccessUploadFileCount:").append(
            getSuccessUploadFileCount()).append(",")
        .append("Status:'").append(getStatus()).append("',")
        .append("ProcessStartTime:").append(getProcessStartTime()).
        append(",")
        .append("ProcessEndTime:").append(getProcessEndTime()).append(
            ",")
        .append("ProcessRunningTime:").append(getProcessRunningTime()).
        append(",")
        .append("Cancel:").append(getCancel()).append("}");
    return strJSon.toString();
  }
}

  2.1.2. 文件上传状态侦听类(FileUploadListener)

   使用Common-FileUpload 1.2版本(20070103)。此版本提供了能够监视文件上传情况的ProcessListener接口,使开发者通过FileUploadBase类对象的setProcessListener方法植入自己的Listener。 FileUploadListener类实现了ProcessListener,在整个文件上传过程中,它对上传进度进行监控,并且根据上传 情况实时的更新上传状态Bean。源代码如下:

/**
 * 本例程演示了通过Web上传文件过程中的进度显示。您可以对本例程进行任何修改和使用。
 * 如果需要转载本例程,请您注明作者。
 *
 * 作者: 刘作晨
 * EMail:liuzuochen@gmail.com
 */
package liuzuochen.sample.upload;
import org.apache.commons.fileupload.ProgressListener;
import javax.servlet.http.HttpServletRequest;
public class FileUploadListener implements ProgressListener{
	private HttpServletRequest request=null;
	public FileUploadListener(HttpServletRequest request){
		this.request=request;
	}
	/**
	 * 更新状态
	 */
	public void update(long pBytesRead, long pContentLength, int pItems){
		FileUploadStatus statusBean= BackGroundService.getStatusBean(request);
		statusBean.setUploadTotalSize(pContentLength);
		//读取完成
	  if (pContentLength == -1) {
	    statusBean.setStatus("完成对" + pItems +"个文件的读取:读取了 " + pBytesRead + " bytes.");
	    statusBean.setReadTotalSize(pBytesRead);
	    statusBean.setSuccessUploadFileCount(pItems);
	    statusBean.setProcessEndTime(System.currentTimeMillis());
	    statusBean.setProcessRunningTime(statusBean.getProcessEndTime());
	  //读取中
	  } else {
	    statusBean.setStatus("当前正在处理第" + pItems +"个文件:已经读取了 " + pBytesRead + 
"/" + pContentLength+ " bytes."); statusBean.setReadTotalSize(pBytesRead); statusBean.setCurrentUploadFileNum(pItems); statusBean.setProcessRunningTime(System.currentTimeMillis()); } BackGroundService.saveStatusBean(request,statusBean); } }

  2.1.3. 后台服务类(BackGroundService)

   BackGroundService这个Servlet类负责接收Form Post数据、回应状态轮询请求、处理取消文件上传的请求。 尽管可以把这些功能相互分离开来,但为了简单明了,还是将它们放到Servlet中,只是由不同的方法进行分割。 源代码如下:

/**
 * 本例程演示了通过Web上传文件过程中的进度显示。您可以对本例程进行任何修改和使用。
 * 如果需要转载本例程,请您注明作者。
 *
 * 作者: 刘作晨
 * EMail:liuzuochen@gmail.com
 */
package liuzuochen.sample.upload;

/** * Title: 后台服务 * * Description: 为客户端提供上传及文件传输状态查询服务 * */ import java.io.File; import java.io.IOException; import java.util.List; import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.apache.commons.fileupload.FileItem; import org.apache.commons.fileupload.FileUploadException; import org.apache.commons.fileupload.disk.DiskFileItemFactory; import org.apache.commons.fileupload.servlet.*; public class BackGroundService extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet { public static final String UPLOAD_DIR = "/upload"; public static final String DEFAULT_UPLOAD_FAILURE_URL = "./result.jsp"; public BackGroundService() { super(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request, response); } /** * 从文件路径中取出文件名 */ private String takeOutFileName(String filePath) { int pos = filePath.lastIndexOf(File.separator); if (pos > 0) { return filePath.substring(pos + 1); } else { return filePath; } } /** * 从request中取出FileUploadStatus Bean */ public static FileUploadStatus getStatusBean( HttpServletRequest request) { BeanControler beanCtrl = BeanControler.getInstance(); return beanCtrl.getUploadStatus(request.getRemoteAddr()); } /** * 把FileUploadStatus Bean保存到类控制器BeanControler */ public static void saveStatusBean( HttpServletRequest request, FileUploadStatus statusBean) { statusBean.setUploadAddr(request.getRemoteAddr()); BeanControler beanCtrl = BeanControler.getInstance(); beanCtrl.setUploadStatus(statusBean); } /** * 删除已经上传的文件 */ private void deleteUploadedFile(HttpServletRequest request) { FileUploadStatus satusBean = getStatusBean(request); for (int i = 0; i < satusBean.getUploadFileUrlList().size(); i++) { File uploadedFile = new File(request.getRealPath(UPLOAD_DIR) + File.separator + satusBean.getUploadFileUrlList(). get(i)); uploadedFile.delete(); } satusBean.getUploadFileUrlList().clear(); satusBean.setStatus("删除已上传的文件"); saveStatusBean(request, satusBean); } /** * 上传过程中出错处理 */ private void uploadExceptionHandle( HttpServletRequest request, String errMsg) throws ServletException, IOException { //首先删除已经上传的文件 deleteUploadedFile(request); FileUploadStatus satusBean = getStatusBean(request); satusBean.setStatus(errMsg); saveStatusBean(request, satusBean); } /** * 初始化文件上传状态Bean */ private FileUploadStatus initStatusBean(HttpServletRequest request) { FileUploadStatus satusBean = new FileUploadStatus(); satusBean.setStatus("正在准备处理"); satusBean.setUploadTotalSize(request.getContentLength()); satusBean.setProcessStartTime(System.currentTimeMillis()); satusBean.setBaseDir(request.getContextPath() + UPLOAD_DIR); return satusBean; } /** * 处理文件上传 */ private void processFileUpload(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { DiskFileItemFactory factory = new DiskFileItemFactory(); //设置内存缓冲区,超过后写入临时文件 factory.setSizeThreshold(10240000); //设置临时文件存储位置 factory.setRepository(new File(request.getRealPath("/upload/temp"))); ServletFileUpload upload = new ServletFileUpload(factory); //设置单个文件的最大上传值 upload.setFileSizeMax(102400000); //设置整个request的最大值 upload.setSizeMax(102400000); upload.setProgressListener(new FileUploadListener(request)); //保存初始化后的FileUploadStatus Bean saveStatusBean(request, initStatusBean(request)); String forwardURL = ""; try { List items = upload.parseRequest(request); //获得返回url for (int i = 0; i < items.size(); i++) { FileItem item = (FileItem) items.get(i); if (item.isFormField()) { forwardURL = item.getString(); break; } } //处理文件上传 for (int i = 0; i < items.size(); i++) { FileItem item = (FileItem) items.get(i); //取消上传 if (getStatusBean(request).getCancel()) { deleteUploadedFile(request); break; } //保存文件 else if (!item.isFormField() && item.getName().length() > 0) { String fileName = takeOutFileName(item.getName()); File uploadedFile = new File(request.getRealPath(UPLOAD_DIR) + File.separator + fileName); item.write(uploadedFile); //更新上传文件列表 FileUploadStatus satusBean = getStatusBean(request); satusBean.getUploadFileUrlList().add(fileName); saveStatusBean(request, satusBean); Thread.sleep(500); } } } catch (FileUploadException e) { uploadExceptionHandle(request, "上传文件时发生错误:" + e.getMessage()); } catch (Exception e) { uploadExceptionHandle(request, "保存上传文件时发生错误:" + e.getMessage()); } if (forwardURL.length() == 0) { forwardURL = DEFAULT_UPLOAD_FAILURE_URL; } request.getRequestDispatcher(forwardURL).forward(request, response); } /** * 回应上传状态查询 */ private void responseStatusQuery(HttpServletRequest request, HttpServletResponse response) throws IOException { response.setContentType("text/xml"); response.setHeader("Cache-Control", "no-cache"); FileUploadStatus satusBean = getStatusBean(request); response.getWriter().write(satusBean.toJSon()); } /** * 处理取消文件上传 */ private void processCancelFileUpload(HttpServletRequest request, HttpServletResponse response) throws IOException { FileUploadStatus satusBean = getStatusBean(request); satusBean.setCancel(true); saveStatusBean(request, satusBean); responseStatusQuery(request, response); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { boolean isMultipart = ServletFileUpload.isMultipartContent(request); if (isMultipart) { processFileUpload(request, response); } else { request.setCharacterEncoding("UTF-8"); if (request.getParameter("uploadStatus") != null) { responseStatusQuery(request, response); } if (request.getParameter("cancelUpload") != null) { processCancelFileUpload(request, response); } } } }

  2.1.4. 文件上传状态控制类(BeanControler)

   这是一个单例类,它的功能是为客户端保存文件上传状态,这里我没有使用Session来存储文件上传状态,因为对于AJAX这种异步调用,服务器会开启不同的Session,所以无法通过Session保存文件上传状态。 我并不认为这种方法最好,如果有更好的方法,欢迎大家一起讨论。 源代码如下:

/**
 * 本例程演示了通过Web上传文件过程中的进度显示。您可以对本例程进行任何修改和使用。
 * 如果需要转载本例程,请您注明作者。
 *
 * 作者: 刘作晨
 * EMail:liuzuochen@gmail.com
 */
package liuzuochen.sample.upload; /** * Title: 类控制器 * * Description: 主要作用是对FileUploadStatus进行管理,为客户端提供相应的 * FileUploadStatus类对象。这是一个单例类。 * */ import java.util.Vector; public class BeanControler { private static BeanControler beanControler = new BeanControler(); private Vector vector = new Vector(); private BeanControler() { } public static BeanControler getInstance() { return beanControler; } /** * 取得相应FileUploadStatus类对象的存储位置 */ private int indexOf(String strID) { int nReturn = -1; for (int i = 0; i < vector.size(); i++) { FileUploadStatus status = (FileUploadStatus) vector.elementAt(i); if (status.getUploadAddr().equals(strID)) { nReturn = i; break; } } return nReturn; } /** * 取得相应FileUploadStatus类对象 */ public FileUploadStatus getUploadStatus(String strID) { return (FileUploadStatus) vector.elementAt(indexOf(strID)); } /** * 存储FileUploadStatus类对象 */ public void setUploadStatus(FileUploadStatus status) { int nIndex = indexOf(status.getUploadAddr()); if ( -1 == nIndex) { vector.add(status); } else { vector.insertElementAt(status, nIndex); vector.removeElementAt(nIndex + 1); } } /** * 删除FileUploadStatus类对象 */ public void removeUploadStatus(String strID){ int nIndex = indexOf(strID); if(-1!=nIndex) vector.removeElementAt(nIndex); } }

 2.2. 客户端代码

   客户端我们采用Prototype框架。请下载。

  2.2.1. AjaxWrapper.js

   AjaxWrapper.js对Prototype进行了封装。请下载分析

  2.2.2. fileUpload.html

   fileUpload.html是文件上传界面。 请下载。

  2.2.3. result.jsp

   result.jsp是文件上传结果显示界面。 请下载

  2.2.4. fileUpload.css

   fileUpload.css是样式文件。 源代码如下:

body {
  color:#000;
  background-color:white;
  font:15px Georgia, "Lucida Grande", Arial, sans-serif;
  letter-spacing:0.01em;
  margin:15px;
}
#controlPanel,#resultPanel{
  width:700px;
  margin:20px auto;
  padding:25px;
  border:3px solid gray;
  -moz-border-radius:10px;
  background:#f8f8f8;
}
#errorArea{
   width:400px;
  margin:20px auto;
  padding:25px;
  border:3px solid gray;
  -moz-border-radius:10px;
  background:red;
}
#normalMessageArea{
  width:400px;
  margin:20px auto;
  padding:25px;
  border:3px solid gray;
  -moz-border-radius:10px;
  background:yellow;
}
#progressBar { padding-top: 5px; }
  #totalProgressBarBox {
   width: 350px;
   height: 20px;
   border: 1px inset;
   background: #eee;
}
#totalProgressBarBoxContent {
  width: 0;
  height: 20px;
  border-right: 1px solid #444;
  background: #9ACB34;
}

 2.3. 配置文件

   web.xml中完成Servlet的配置。

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<display-name>AjaxPractice</display-name>
<servlet>
  <description></description>
  <display-name>BackGroundService</display-name>
  <servlet-name>BackGroundService</servlet-name>
  <servlet-class>liuzuochen.sample.upload.BackGroundService</servlet-class>
</servlet>

<servlet-mapping>
  <servlet-name>BackGroundService</servlet-name>
  <url-pattern>*.action</url-pattern>
</servlet-mapping>
<welcome-file-list>
  <welcome-file>index.html</welcome-file>
   <welcome-file>index.htm</welcome-file>
  <welcome-file>index.jsp</welcome-file>
  <welcome-file>default.html</welcome-file>
  <welcome-file>default.htm</welcome-file>
  <welcome-file>default.jsp</welcome-file>
</welcome-file-list>
</web-app>

 3. 结语

   整个程序到这里就介绍完了,希望它多少能为您的工作或学习带来点儿帮助。

以上就是【AJAX和javascriptP实现的基于WEB的文件上传的进度控制代码】的全部内容了,欢迎留言评论进行交流!

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